Partial Purification and Product Specificity of Adzukibean Lipoxygenase

Abstract

Lipoxygenase (EC 1. 13. 11. 12) from adzukibeans was partially purified and some characteristics were examined to understand the mechanism by which the stale cooked flavor was formed in stored adzukibeans. The adzukibean enzyme specifically acted on the free form of polyunsaturated fatty acids and was more labile than soybean enzyme (L-1 type). Incubation of linoleic acid with this enzyme yielded 13- to 9- hydroperoxides at a ratio of 48:52. The adzukibean enzyme, which has the optimum pH around 6.5 and is activated by calcium ion, is different from soybean (L-1 type) and rice germ enzymes in the composition of hydroperoxide isomers formed, and similar to the soybean isozyme (L-2 type), which is reported to play a main role in the development of n-hexanal in soybean flavors.